1. Field of the Invention
The present invention relates to a method for manufacturing an active-matrix display device. More specifically, the invention relates to a method for forming a structure of a part for extracting luminescence generated from a light emitting element in a display device having the light emitting element.
2. Description of the Related Art
A display device using luminescence generated from an electroluminescence element (a light emitting element) has drawn attention as a display device with a high viewing angle and low power consumption.
A driving method of a display device mainly used for displaying includes ones of an active-matrix type and a passive-matrix type. In a display device using the active-matrix-type driving method, emission state, non-emission state, or the like can be controlled per a light emitting element. Therefore, the active-matrix display device can be driven in lower power consumption than a passive-matrix display device; accordingly, it is suitable for a display portion of a large-sized display such as a television receiver as well as a display portion of a small-sized one such as a portable phone.
In addition, in the active-matrix display device, a circuit for controlling driving of each light emitting element is provided in each light emitting element. The circuit and the light emitting element are disposed over a substrate so that the circuit does not prevent luminescence from being extracted outside. Light-transmitting insulating layers are stacked in a portion overlapping the light emitting element, and luminescent is emitted outside through the insulating layer. The insulating layers are disposed in order to form a circuit element such as a transistor or a capacitor element which is a component of a circuit or to form a wiring.
In some cases, a multiple interaction of luminescence may occur due to the difference in a refractive index of each insulating layer when the luminescence passes through the stacked insulating layers. As a result, an emission spectrum varies depending on an angle to a light emitting surface, thereby causing deterioration in visibility of an image displayed in a display device.
In addition, the deterioration in visibility of an image due to the difference in a refractive index of each layer also occurs in a passive-matrix display device. For example, Patent Document 1: Japanese Patent Laid-Open No. Hei7-211458 raises a problem in which the deterioration in visibility is caused since external light and luminescence are reflected at an interface due to the difference in a refractive index of each layer which constitutes a part of a light emitting element. Patent Document 1 also suggests a light emitting element with a devised element structure capable of solving the above problem.